The present invention is directed to methods for preparing colorant compounds. More specifically, the present invention is directed to processes for preparing colorant compounds particularly suitable for use in hot melt or phase change inks. One embodiment of the present invention is directed to a process for preparing a colorant of the formula
wherein Y is a hydrogen atom or a bromine atom, n is an integer of 0, 1, 2, 3, or 4, R1 is an alkylene group or an arylalkylene group, R2 is an alkyl group, an aryl group, an arylalkyl group, or an alkylaryl group, and R4 is an alkyl group, an aryl group, an arylalkyl group, or an alkylaryl group, can be prepared by a process which comprises (a) preparing a first reaction mixture by admixing (1) leucoquinizarin and, optionally, quinizarin, (2) an aminobenzene substituted with an alcohol group of the formula —R1—OH, (3) boric acid, and (4) an optional solvent, and heating the first reaction mixture to prepare an alcohol-substituted colorant of the formula
followed by (b) converting the colorant thus prepared to either (i) an ester-substituted colorant by reaction with an esterification compound which is either (A) an anhydride of the formula
or (B) an acid of the formula R2COOH in the presence of an optional esterification catalyst, or
(ii) a urethane-substituted colorant by reaction with an isocyanate compound of the formulaR4—N═C═O,and (c) brominating the colorant thus prepared, wherein either conversion to ester or urethane can be performed before bromination or bromination can be performed before conversion to ester or urethane.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. No. 4,889,560, U.S. Pat. No. 4,889,761, and U.S. Pat. No. 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes. The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Phase change inks have also been used for applications such as postal marking and industrial marking and labelling.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Compositions suitable for use as phase change ink carrier compositions are known. Some representative examples of references disclosing such materials include U.S. Pat. No. 3,653,932, U.S. Pat. No. 4,390,369, U.S. Pat. No. 4,484,948, U.S. Pat. No. 4,684,956, U.S. Pat. No. 4,851,045, U.S. Pat. No. 4,889,560, U.S. Pat. No. 5,006,170, U.S. Pat. No. 5,151,120, U.S. Pat. No. 5,372,852, U.S. Pat. No. 5,496,879, European Patent Publication 0187352, European Patent Publication 0206286, German Patent Publication DE 4205636AL, German Patent Publication DE 4205713AL, and PCT Patent Application WO 94/04619, the disclosures of each of which are totally incorporated herein by reference. Suitable carrier materials can include paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, fatty acids and other waxy materials, fatty amide containing materials, sulfonamide materials, resinous materials made from different natural sources (tall oil rosins and rosin esters, for example), and many synthetic resins, oligomers, polymers, and copolymers.
U.S. Pat. No. 6,395,078 (Jaeger), U.S. Pat. No. 6,422,695 (Jaeger), Canadian Patent Publication 2 355 533 (filed Aug. 20, 2001, published Feb. 23, 2002), European Patent Publication EP1 182 232 (filed Aug. 17, 2001, published Feb. 27, 2001), Japanese Patent Publication JP 2002129044 (filed Aug. 8, 2001, published May 9, 2002), Brazilian Patent Publication P101035819 (filed Aug. 22, 2001, published Mar. 26, 2002), and Mexican Patent Application 2001008418 (filed Aug. 20, 2001), the disclosures of each of which are totally incorporated herein by reference, disclose a compound having the formula
wherein at least one Q1, Q2, Q3, and Q4 is a halogen atom and any of Q1, Q2, Q3 and Q4 which is not a halogen atom is a hydrogen atom; and wherein R comprises at least two carbon atoms. The invention further encompasses inclusion of such compound into phase change ink carrier compositions, as well as printing methods utilizing such compound.
British Patent Publication GB 2 021 138 (Hohmann et al.), the disclosure of which is totally incorporated herein by reference, discloses mixtures of dyestuffs of the formula
and of the formula
wherein R1, R2, and R3 denote C1-C4 alkyl, C1-C4 alkoxy, or halogen, and n denotes 2 or 3, which are suitable for dyeing polyester fibers by the exhaustion process. Dark blue and navy blue dyeings with good fastness properties are obtained.
U.S. Pat. No. 6,174,937 (Banning et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink comprising a material of the formula
wherein X1, X2, X3 and X4 are segments comprising atoms selected from groups V and VI of the periodic table; wherein at least one R1 and R5 comprises at least 37 carbon units; and wherein R2, R3 and R4 each comprise at least one carbon unit. The invention further encompasses a composition of matter, as well as methods of reducing coefficients of friction of phase change ink formulations.
U.S. Pat. No. 5,507,864 (Jaeger et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink composition that includes a combination of different dye types such as an anthraquinone dye and a xanthene dye, which is most preferably a rhodamine dye. While each dye type is insufficiently soluble with respect to favored carrier compositions to preserve color saturation in reduced ink quantity prints, the dye type combination permits increased dye loading and maintains print quality. In a preferred embodiment of the invention, a favored carrier composition is adjusted to promote the colored form of a preferred rhodamine dye (C.I. Solvent Red 49) and mixed with a preferred anthraquinone dye (C.I. Solvent Red 172) whose concentration is kept below a critical level to prevent post printed blooming. The resulting preferred phase change ink compositions provide a magenta phase change ink with enhanced light fastness and color saturation, as well as good compatibility with preferred existing subtractive primary color phase change inks.
U.S. Pat. No. 5,902,841 (Jaeger et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink composition wherein the ink composition utilizes a colorant in combination with a selected phase change ink carrier composition containing at least one hydroxy-functional fatty amide compound.
R. Butnaru et al., “Researches on Dyeing of Cotton Fabrics with Acid Dyestuffs, Concomitantly with Crease-Resist Treatments,” Cellulose Chem. Technol., 29, p. 471 (1995), the disclosure of which is totally incorporated herein by reference, discloses an analysis of the results obtained on dyeing of cotton cellulosic fabrics with acid dyestuffs, on employing crease-resist agents with polyfunctional structure. The conclusion was reached that no chemical or physical bonds occur between dyestuffs and the fiber, the dyestuffs being fixed onto the resin's aminic groups formed as a result of the thermal, crease-resist treatment. Washing resistance of the cellulosic materials thus dyed attained the values obtained as a result of dyeing with direct dyestuffs, specific for these types of fibers.
U.S. Pat. No. 6,235,094 (Banning et al.), the disclosure of which is totally incorporated herein by reference, discloses a compound having the formula
wherein R1, Z and the carbonyl can be comprised by a common ring, wherein R1 comprises a chromophore that absorbs light from the visible wavelength range, and wherein n is an integer that is at least 12. The invention also encompasses a solid phase change ink composition. Such composition includes a phase change ink carrier and a colorant. The colorant comprises a chromophore that absorbs light from the visible wavelength range, and has the formula
wherein R1, Z and the carbonyl can be comprised by a common ring, wherein n is an integer that is at least 12. Additionally, the invention encompasses a method of forming a colorant. A first compound having the formula
is reacted with a second compound having the formula Z(CH2)nCH3, wherein n is an integer that is at least 12, to form a third compound having the formula
wherein the third compound comprises a chromophore that absorbs light from the visible wavelength range.
While known compositions and processes are suitable for their intended purposes, a need remains for improved colorant compounds. In addition, a need remains for colorant compositions particularly suitable for use in phase change inks. Further, a need remains for colorant compounds with a desirable magenta color. Additionally, a need remains for colorant compounds with desirable thermal stability. There is also a need for colorant compounds with good lightfastness. In addition, there is a need for colorant compounds that exhibit desirable solubility characteristics in phase change ink carrier compositions. Further, there is a need for colorant compounds that, when incorporated into phase change inks, exhibit reduced migration within a layer of printed ink. Additionally, there is a need for colorant compounds that, when incorporated into phase change inks, exhibit reduced crystallization within a layer of printed ink. A need also remains for colorant compounds that, when incorporated into phase change inks, enable production of prints that maintain uniform color over long periods of time without unevenness or blotching. In addition, a need remains for colorant compounds that, when incorporated into phase change inks, enable production of prints that retain their original color over long periods of time. Further, a need remains for colorant compounds that, when incorporated into phase change inks, enable production of prints that exhibit reduced sensitivity to image discoloration upon contact with human fingertips. Additionally, a need remains for colorant compounds that can be incorporated into phase change inks in desirably high concentrations. There is also a need for colorant compounds that can be manufactured easily and practically. In addition, there is a need for colorant compounds that can easily be converted to derivative molecules thereof.